الفهرس 
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Abstract
English Abstract:
Natural products have been used to treat diseases since ancient times. Modern medicine includes hundreds of preparations that were discovered and developed from natural sources, of both terrestrial and marine origin. The main objective of this thesis was to perform LC-HRESIMS-assisted dereplication along with isolation and structure elucidation of secondary metabolites from four natural sources; the plant Phagnalon rupestre Family Asteraceae, the Red Sea soft coral Rumphella torta, and the two Red Sea sponges, Stylissa carteri and Echinoclathria sp.
Bioassay-guided fractionation together with LC-HRESIMS-assisted chemical investigation of Phagnalon rupestre led to the isolation of a known metabolite which was isolated for the first time from Phagnalon rupestre, β sitosterol-3-O-β-D-glucopyranoside (1) and another known metabolite, 12-O- β-glucopyranosyl-9 β,12-dihydroxytremetone (2).
Chromatographic techniques together with LC-HRESIMS-assisted chemical investigation of the Red Sea soft coral Rumphella torta led to the isolation and structure elucidation of eight known compounds; Cholesterol (3), four fatty acids, namely Myristic acid (4), Palmitic acid (5), Arachidic acid (6) and Stearic acid (7), in addition to chimyl alcohol (8), Hexadecanoic acid 2,3-dihydroxy-propyl ester (9) and Thymine (10). All the isolated compounds were isolated for the first time from this species.
Chromatographic techniques together with LC-HRESIMS-assisted chemical investigation of the Red Sea sponge Stylissa carteri led to the isolation and structure elucidation of two new compounds; a ceramide, stylissamide (11), and a cerebroside, stylissoside (12).
Moreover, Chemical investigation of the Red Sea sponge Echinoclathria sp. led to the isolation and structure elucidation of one known compound which was isolated for the first time from Echinoclathria sp, 2β,18-dihydroxy-15α-acetoxy-5,6,7,8-tetrahydroergosterol (thalassosterol). (13), and a new sterol, Butyric acid 1-[1 acetoxy-2-(15-acetoxy-2,3,16-trihydroxy-10,13-dimethyl-hexadecahydro-cyclopenta [a] phenanthren-17-yl)-propyl]-2,3-dimethyl-butyl ester and named, Echinosterol. (14).
The structures of the metabolites were determined by extensive spectroscopic analysis including 1D, 2D NMR and mass spectroscopy.
Phagnalon rupestre extract and its fractions were tested for their affinity for opioid and cannabinoid receptors. The plant extract showed higher than 40% affinity, and fractions 2, 5, and 6 were also active. Fraction 2 showed selectivity for the delta opioid receptor subtype, while fraction 5 showed affinity for both opioid and cannabinoid receptors. Fraction 6 showed affinity for cannabinoid but not for opioid receptors.
Potential cytotoxic activities of compounds 11, 12, 13, and 14 were measured by the Sulpho-Rhodamine-B (SRB) assay. The in-vitro cytotoxic activity of compounds 11 and 12 was tested against two human cancer cell lines, the breast cancer cell line MCF-7 and the liver cancer cell line HepG2. Cytotoxic activity of compounds 13 and 14 was tested against three human cancer cell lines, MCF-7, HepG2 and the cervical cancer cell line HeLa. Compounds 11 and 12 displayed strong cytotoxicity against the MCF-7 cell line, with IC50 values at 21.1 µM and 27.5 µM, respectively. In addition, they showed promising activity against HepG2 with IC50 at 36.8 µM and IC50 30.5 µM, respectively compared to the standard drug cisplatin. Compounds 13 and 14 displayed strong cytotoxicity against the HeLa cell line, with IC50 at 3.98 and 3.23 µM, respectively, also the two compounds showed significant activity against HepG2 cancer cells with IC50 values of 23.8 µM and 28.1 µM, respectively. Concerning MCF-7, Compound 13 exhibited stronger cytotoxicity with an IC50 value of 6.98 µM, while compound 14 displayed a promising cytotoxicity, with an IC50 value of 16.6 µM compared to the standard drug doxorubicin.
Moreover, a docking study was performed to investigate the possible mechanism(s) of the cytotoxic activity of 11 and 12. The two compounds displayed high affinity to the SET protein and to inhibitor 2 of protein phosphatase 2A (I2PP2A), which could be a possible mechanism for their cytotoxic activity. This study sheds the light on the role of these metabolites in keeping fouling organisms away from the outer surface of the sponge, and the possible applications of these defensive molecules in the development of new anticancer drugs.
Key words: Asteraceae, Phagnalon rupestre, Red Sea, soft corals, Rumphella torta, sponges, Stylissa carteri, Echinoclathria sp., ceramide, cerebroside, LC-HRESIMS, anticancer, cannabinoid, opioid, PP2A.